.\" Copyright 2012, Cyrill Gorcunov <gorcunov@openvz.org>
.\" Copyright 2012, 2013, 2015, Michael Kerrisk <mtk.manpages@gmail.com>
.\" Copyright 2024, Alejandro Colomar <alx@kernel.org>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH PR_SET_MM_EXE_FILE 2const 2024-06-01 "Linux man-pages 6.9.1"
.SH NAME
PR_SET_MM_EXE_FILE
\-
modify kernel memory map descriptor fields
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.BR "#include <linux/prctl.h>" "  /* Definition of " PR_* " constants */"
.B #include <sys/prctl.h>
.P
.BI "int prctl(PR_SET_MM, PR_SET_MM_EXE_FILE, long " fd ", 0L, 0L);"
.fi
.SH DESCRIPTION
Supersede the
.IR /proc/ pid /exe
symbolic link with a new one pointing to a new executable file
identified by the file descriptor provided in the
.I fd
argument.
The file descriptor should be obtained with a regular
.BR open (2)
call.
.P
To change the symbolic link, one needs to unmap all existing
executable memory areas, including those created by the kernel itself
(for example the kernel usually creates at least one executable
memory area for the ELF
.I .text
section).
.SH RETURN VALUE
On success,
0 is returned.
On error, \-1 is returned, and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EACCES
The file is not executable.
.TP
.B EBADF
The file descriptor passed in
.I fd
is not valid.
.TP
.B EBUSY
This the second attempt to change the
.IR /proc/ pid /exe
symbolic link.
.SH FILES
.TP
.IR /proc/ pid /exe
.SH STANDARDS
Linux.
.SH HISTORY
Linux 3.5.
.\" commit b32dfe377102ce668775f8b6b1461f7ad428f8b6
.P
In Linux 4.9 and earlier, the
.\" commit 3fb4afd9a504c2386b8435028d43283216bf588e
.B PR_SET_MM_EXE_FILE
operation can be performed only once in a process's lifetime;
attempting to perform the operation a second time results in the error
.BR EPERM .
This restriction was enforced for security reasons that were subsequently
deemed specious,
and the restriction was removed in Linux 4.10 because some
user-space applications needed to perform this operation more than once.
.SH SEE ALSO
.BR prctl (2),
.BR PR_SET_MM (2const),
.BR proc_pid_exe (5)
